In wellbore drilling operations, a drilling fluid is flowed from a surface through a drill string and into a drill bit drilling the formation. The drilling fluid flows through the drill bit and returns to the surface through an annulus formed between the side walls of the wellbore and the drill string. Rheological properties of the drilling fluid affect the effectiveness of the wellbore drilling operation. For example, a change in viscosity of the drilling fluid can be an indication that certain additives to the drilling fluid have been lost to the formation and need to be replenished.